Advice on 70-300mm lens - looking at 4 different ones.

I had the non-DO and then went to the DO. Differences, DO was more compact and handled easier. The non-DO was sharper initially once I got it back from Canon to fix a documented issue on focus. DO is extreme sharp after applying sharpening in workflow. DO focuses very noticably faster. Love build quality on DO. Non-DO was noticably cheaper. Trade-offs and you have to decide which are most important. I am extremely satisfied with the DO and would make the same decision again.
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